A number of devices have been previously used in currency dispensing machines to measure the thickness of the bills dispensed and to detect folded or overlapped bills. U.S. Pat. No. 4,154,437 owned by the assignee of the present invention discloses apparatus for detecting the presence of folded or overlapped sheets. This apparatus comprises a pair of adjacent cooperating rolls. The first roll of the pair is mounted on a relatively thick, rigid shaft. The second roll of the pair is mounted on a relatively thin, flexible shaft. The bills are passed between the rolls generally one at a time. As bills are passed between the rolls, the second roll which is mounted on the flexible shaft is deflected an amount proportional to the thickness of the bill. By sensing the deflection of the second roll, the thickness of the bill is determined. The apparatus disclosed in the patent averages thickness over the entire length of the bill. Averaging thickness avoids the rejection of bills which may be slightly thicker in portions than normal bills.
U.S. Pat. No. 4,462,587, also owned by the assignee of the present invention, utilizes similar thickness sensing apparatus. The invention disclosed in this patent however, involves a method for utilizing the thickness measurements obtained from the sensor to determine the particular status of the bills detected such as single bills, overlapped double bills, etc. According to the invention of this patent, once the condition of the bill(s) is identified the bill(s) are either dispensed or withheld from being dispensed depending on the number of bill(s) requested by the individual operating the currency dispensing machine or ATM.
The thickness indicating apparatus disclosed in both U.S. Pat. Nos. 4,154,437 and 4,462,587 has the inherent disadvantage that it senses thickness at only one location across the bill, normally along the center line of the bill path. Bills which are folded or skewed may fail to pass through the rolls which results in such bills being dispensed undetected. The cooperating pair of rolls require considerable space which limits where they can be positioned inside the bill dispensing apparatus. In addition, due to the high precision required of the components for the thickness sensing apparatus, it is expensive to manufacture.
Other types of thickness indicating apparatus have been previously used as thickness detectors. Photoelectric devices which determine bill thickness by measuring the amount of light which will pass through a bill and capacitance sensors which determine bill status based on the varying electrical characteristics of single/double bills, etc., have been previously utilized. These devices all have the same inherent disadvantage in that they sense thickness at only one location across the bill and miss certain skewed or folded bills. Such devices are also subject to failure due to build-up of dirt on the sensors, which occurs frequently when used currency is dispensed. A further drawback is that such devices are expensive. Because the amount of light transmitted as well as capacitance varies substantially between new and used bills, such devices are generally less reliable than mechanical sensors.
The problem of skewed or folded bills missing a thickness sensing apparatus is minimized when bills are transported lengthwise; that is with the short side leading as was the case with the bill transports shown in U.S. Pat. Nos. 4,154,437 and 4,462,587. The probability of a failure to detect a bill is increased when bills are transported laterally with the long side leading, as in such circumstances bills have a greater tendency to skew and fold during transport.
Thus there exists a need for a thickness indicator apparatus that detects the thickness of bills transported laterally in a transport path, which bills may be located in a plurality of locations across the width of a transport path; is less susceptible to failure to detect skewed or folded bills; operates in a limited space; is more reliable; and is less expensive than thickness sensing apparatus presently available.